The disclosure relates to studying physical properties of heterogeneous materials and can be used for analyzing texture, structure, porosity, thermal conductivity, thermal diffusivity, and volumetric heat capacity of geomaterials, constructional and other natural and industrial materials in different science and technology areas.
There is a known method and apparatus fir determining thermal conductivity and thermal diffusivity described in article “New methods and instruments for determination of reservoir thermal properties,” by Popov, Yu., Bayuk, I., Parshin, A., Miklashevskiy, D., Novikov, S., Chekhonin, E. and Proceedings, Thirty-Seventh Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, Calif., Jan. 30-Feb. 1, 2012, SGP-TR-194. In the known apparatus, a first sensor records a temperature of a heated surface of a sample of a heterogeneous material and of samples with known thermal conductivity and thermal diffusivity along a heating line at a distance X1 from a moving heating spot created by a heater. A second temperature sensor is installed at the same distance X1 from the heating spot, along the heating line, and at a distance Yo from the heating line and records surface temperatures of the sample of the heterogeneous material and of the samples with known thermal conductivity and thermal diffusivity along a line parallel to the heat spot trajectory and located at the distance Yo from it. A third sensor records an initial temperature of the sample of the heterogeneous material and the samples with known thermal conductivity and thermal diffusivity along the heating line and is installed along the heating spot trajectory, in front of the heating spot, at an arbitrary distance X2 from it.
These known method and apparatus has such disadvantages as a need to return a unit with the heater and the temperature sensors to the initial position for the next measurement; in this process, when the unit with the heater and the temperature sensors are returned to the initial position, no measurements are carried out, which results in nonproductive time. Besides, within a single measurement cycle including scanning of the samples in a forward direction and return of the unit with the heater and the temperature sensors to the initial position, it is not possible to measure thermal conductivity for sample layers with different thickness and width, i.e. it is impossible to determine thermal conductivity for layers with different thickness and width in a heterogeneous sample, which is important for describing heterogeneity of the samples. It is also impossible to obtain high-detail profiles of thermal conductivity distribution along the scanning line with a high spatial resolution. This is due to the fact that such high-detail measurements require maximal decrease of the distance X1 between the sensors measuring sample surface heating temperature and the heating spot, which results in unacceptable decrease in a thickness of a layer of the heterogeneous sample and appropriate decrease in a volume of the heterogeneous sample. Besides, significant decrease in the distance X1 results in a loss of accuracy of thermal conductivity and thermal diffusivity measurements because the actual heating spot cannot be considered as a point heating source taken as a basis for a theoretical model of measuring thermal conductivity and thermal diffusivity by this method. Then, in case of significant decrease in the distance X1, heating temperature within an area of its registration by the second sensor becomes so low that the second sensor will record it with inadmissible signal-to-noise ratio, which will result in loss of opportunity for high quality measurements of thermal diffusivity. Besides, a maximal decrease in the distance X1 results in significant decrease in temperature registered by the second temperature sensor, which results in an extremely low accuracy of thermal diffusivity measurements and, as a consequence, to a loss of opportunity for high-quality measurements of thermal diffusivity. One more disadvantage of the known method is that thermal conductivity and thermal diffusivity measurements and registration of heterogeneity of the heterogeneous material sample are carried out only along one scanning line, which restricts information on a degree, nature, and spatial distribution of material heterogeneity and quality of data on its thermal conductivity and thermal diffusivity.